The present invention relates, in general, to the controlled heating or cooling of small plate-like objects, particularly those made with semiconductor materials and, in particular to a new and useful method and apparatus for heating or cooling small plate-like objects which utilizes a differential pressure between upper and lower surfaces of the object to retain the object against a heated or cooled carrier member.
The state of the art includes attempts to improve heat transmission, by radiation, convection and conduction. A convex curved clamping plate, to which a semiconductor plate is attached, is disclosed in U.S. Pat. No. 4,282,924. The cooling or heating performance of this installation is limited by its dimensions. Only the rear side of a small plate of this installation, is in contact with the heat conducting surface. On a microscopic level, only small areas of the surface in question (in a typical case less than 5%) are really in contact with each other.
Using gas pipe techniques (in German "Gasleitung") it is known, that heat coupling between two adjacent surfaces is possible. In U.S. Pat. No. 4,457,359 (equivalent to German patent application No. 33 17 967) the advantages of heat transmission by way of a gas pipe, have been combined with the advantages of solid bodies. For this purpose a convex back plate is used and the semiconductor plate is prestressed with a stretching device at the edge of this back plate, so that a high gas pressure can be used without curving the semiconductor plate.
This measure permits the smallest possible distance between the small plate and the back plate, in spite of the optimal gas pressure used, by reason of the anterior curvature in the plate. The disadvantage of this, however, lies in the fact that such a curvature of the small plate cannot be accepted, for example, in a silicon wafer with a diameter of less than 4", since this causes a risk of breakage, stress conditions in the layer and tolerance problems in the micro structure of the finished products.